Breast Cancer and High White Blood Cell Count
White blood cells (WBCs), also known as leukocytes, are essential components of the immune system that help protect the body against infections. Produced in the bone marrow, they circulate throughout the body, seeking out and removing harmful bacteria, viruses, and other invading organisms.
To check the amounts of various cell types in the blood, your doctor will order a complete blood count (also called a CBC). High or low white blood cell counts can signal that your body is trying to defend itself. A normal WBC count for adults ranges from about 4,000 to 11,000 cells per microliter of blood. A count below 4,000 is considered low, while a count above 11,000 is considered high.
What causes high white blood cell counts?
There are many different reasons your WBC count may be higher than normal.
White blood cells often surge in response to infection, inflammation, trauma, burns, and illness. Pregnancy, stress, and smoking can also lead to higher levels of WBCs.
White blood cell counts can indicate some cancers, including leukemia, lymphoma, and multiple myeloma. But can WBCs predict breast cancer? For now, the answer is no. That’s because the results of studies exploring a possible link between high WBC and breast cancer have been mixed.
A large study of over 2,700 women with a family history of breast cancer found that higher levels of certain WBCs, like B cells, were linked to a greater risk of developing the disease. In contrast, women with higher levels of WBCs called monocytes had a lower risk of developing breast cancer within the first year after their blood was drawn. These findings suggest that WBC levels may shift before breast cancer appears.
A different study in South Korea looked at 8,804 women, half with breast cancer and half without, using data from a national health survey. The researchers found that WBC counts seemed to change with breast cancer depending on factors like age, body weight, and hormone receptor status.
Researchers say that more research is needed to determine if WBCs can be used to predict cancer risk.
A high WBC count is much more likely to be a side effect of treatment than a sign of breast cancer. Monitoring WBC levels before, during, and after treatment helps doctors understand how your body is responding to treatment.
Breast cancer treatments known to increase WBCs
If you’re being treated for breast cancer, it’s important to be aware that some of your treatments may cause your white blood cell count to go up.
Steroids (such as dexamethasone or prednisone) are often given before chemotherapy to decrease side effects such as nausea, vomiting, inflammation, and fluid retention. Steroids can cause a temporary increase in WBC counts — especially a type of WBCs called neutrophils — by preventing them from leaving the bloodstream. These effects are temporary and usually resolve in a few days after the steroids are discontinued.
These medications (which include Neupogen, Zarxio, and Neulasta) are usually given 24 hours after a chemotherapy infusion to help bone marrow recover and boost WBCs, especially neutrophils. This helps reduce the risk of infection for about 7 to 10 days after chemotherapy. Sometimes these medications work a little too well and cause WBCs to be higher than normal.
If you’re receiving a “dose-dense schedule” of chemo, your WBCs may rise. Dose-dense chemo is when the same dose of chemo is given within a shorter time frame; for instance, chemo every two weeks instead of every three weeks. In order to receive the chemo in a shorter time frame, you’ll likely receive white blood cell-boosting drugs — leading to a rise in WBCs. Less often, having higher WBCs than normal after chemo can be a sign that the body is reacting to infection or inflammation.
Standard breast cancer treatments, such as chemotherapy, radiation, and certain targeted therapies, given without a white blood cell-boosting drug, tend to lead to lower WBCs. If your white blood cell counts are high, providers will need to find the source.
When cancer spreads to other parts of the body, such as the liver, the immune system reacts strongly, even though there’s no infection. This response is called Systemic Inflammatory Response Syndrome (SIRS). The body sends signals that trigger the release of more WBCs. The cancer itself, especially in organs like the liver, can cause enough stress and inflammation to activate this kind of immune response.
Treating high white blood cell counts
“If a patient spikes a fever or feels unwell between treatments, we have to rule out infection first,” says Aarthi Rajkumar, MD, FACP, an oncologist at Aultman Hematology and Oncology in Canton, Ohio. “This usually means running labs, imaging if needed, and starting antibiotics. Sometimes chemotherapy treatment may have to be paused. The immune system needs a chance to recover.”
When infection isn’t the cause, inflammation could be the culprit. “When blood cultures are negative for infection, I give steroids to help cool down the inflammation,” Rajkumar says. “I might also order scans to make sure the cancer hasn’t spread and isn’t causing an inflammatory response. If it has, we may need to adjust the treatment plan.”
Rajkumar says she routinely checks WBC counts in people newly diagnosed with breast cancer, as well as before each round of chemotherapy.
Types of white blood cells
There are five types of white blood cells:
Basophils release chemicals to trigger an allergic reaction and prevent blood clots.
Eosinophils help protect the body from parasites as well as infections caused by fungus, bacteria, and viruses.
Lymphocytes help the body recognize and remember harmful invaders. There are two main types: T cells, which target abnormal cells, and B cells, which produce antibodies to target specific invaders.
Monocytes respond to infections by turning into two types of cells: dendritic cells to call for help, and macrophages to surround and remove germs.
Neutrophils respond to infection by trapping and consuming germs. They also work with other immune cells to heal wounds.
— Last updated on July 26, 2025 at 5:36 PM